THE ACFT WAS 1 OF 2 THAT MADE A LOW PASS OVER RWY 24. AFTER THE PASS, THE PLT MADE A RIGHT TURN, ESTABLISHING THE ACFT IN A RIGHT TRAFFIC PATTERN FOR RWY 24. ACCORDING TO 1 WITNESS, WHILE THE ACFT WAS TURNING ON A RIGHT BASE, INTERMITTENT BURSTS OF DARK SMOKE WERE OBSERVED TRAILING FROM THE ACFT. HE SAID THAT WHEN THE ACFT TURNED ONTO FINAL APCH, THE SMOKE TRAILS BECAME MORE DESTINCT & NUMEROUS. THE ENG THEN BEGAN CUTTING OUT & MISFIRING. SUBSEQUENTLY, THE ACFT TURNED SLIGHTLY TO THE RIGHT & COLLIDED WITH A POWER LINE, THEN IT HIT TREES, CRASHED & BURNED. AN EXAM OF THE ENG REVEALED THE ACCESORY CASE WAS TOTALLY DESTORYED & THE BLOWER CASE HAD MELTED TO THE POINT THAT THE BLOWER WAS EXPOSED. EXCESSIVE HEAT DAMAGE & DISCOLORATION WERE NOTED AT THE MAIN BEARING AREA OF THE MASTER ROD & THE #7 & &8 ARTICULATING ROD BEARINGS. ALSO, RUST & THE LACK OF OIL RESIDUE WAS NOTED IN THESE AREAS. EXTENSIVE FIRE & IMPACT DAMAGE DISRUPTED ENG CONTINUITY & PREVENTED ROTATION OF THE MAJOR MOVING PARTS. TEMP & DEW POINT WERE 92 & 70 DEG.